Free abrasive machining devices or lapping wheels are well known in the art and generally operate by introducing an abrasive to a rotating wheel to smooth a surface of a substantially flat part to be used as a component in a particular device. Free abrasive machines generally comprise a flat annular rotatable wheel on which are disposed a plurality of work stations. Each station is defined by a large heavy retaining ring having an interior space containing workpieces to be machined. The surfaces of the workpieces are machined by the retaining rings holding the workpieces in a given position relative to the rotating wheel. Additional pressure is applied to the workpieces contained within the retaining rings by pressure plates disposed above the retaining rings which fit within the interior diameter of the retaining rings to apply a downward pressure on the workpieces against the rotating wheel. An abrasive usually suspended in some type of liquid is released onto the lapping wheel for grinding and smoothing the pieces.
The loading, unloading and positioning of the pieces on the lapping wheel has in the past been done manually. By performing this operation manually an attendant is required to be stationed by the machine practically at all times. This often causes higher operating expenses in the form of wages, insurance, injuries, inaccuracy, fatigue and the like.
Other attempts at automation have not completely eliminated the need for an operator or have not decreased the down time of the machine needed for loading and unloading the pieces to be machined. For example, the automated loading and unloading means disclosed in Schulz, U.S. Pat. No. 3,443,342, requires several loading and unloading steps of the lapping wheel. Since the lapping wheel laps three wear rings of articles at a time, and since only one ring is loaded or unloaded from the lapping wheel at any one time, the running time of the lapping wheel is one third the total time required to produce a finished article. Consequently, the actual cycle time for lapping a workpiece is increased by the length of time required to load and unload each wear ring. This stopping and starting of the lapping wheel before a workpiece is completely finished, necessarily increases the downtime of the device.